bans on abortion and handguns as examples
Groups supporting bans on abortion and handguns both use the incrementalism approach you mention. Both groups' ultimate goal is politically unpopular, so they support incremental steps instead - "partial birth" abortion, and gun registration. Both groups' opponents trot out the slippery slope argument ad nauseum. We know what the banning groups really want, and that's not on the table.
Considering that we've never quite fallen into the pits of hell everyone keeps promising us, the slipping argument should be despised, and the issue of "partial birth" abortion and gun registration should be argued on their own merits.